Sustainability effects of motor control stabilisation exercises on pain and function in chronic nonspecific low back pain patients: A systematic review with meta-analysis and meta-regression

Study design Systematic review with meta-analysis and meta-regression. Background and objectives We systematically reviewed and delineated the existing evidence on sustainability effects of motor control exercises on pain intensity and disability in chronic low back pain patients when compared with an inactive or passive control group or with other exercises. Secondary aims were to reveal whether moderating factors like the time after intervention completion, the study quality, and the training characteristics affect the potential sustainability effects. Methods Relevant scientific databases (Medline, Web of Knowledge, Cochrane) were screened. Eligibility criteria for selecting studies: All RCTs und CTs on chronic (≥ 12/13 weeks) nonspecific low back pain, written in English or German and adopting a longitudinal core-specific/stabilizing sensorimotor control exercise intervention with at least one pain intensity and disability outcome assessment at a follow-up (sustainability) timepoint of ≥ 4 weeks after exercise intervention completion. Results and conclusions From the 3,415 studies that were initially retrieved, 10 (2 CTs & 8 RCTs) on N = 1081 patients were included in the review and analyses. Low to moderate quality evidence shows a sustainable positive effect of motor control exercise on pain (SMD = -.46, Z = 2.9, p < .001) and disability (SMD = -.44, Z = 2.5, p < .001) in low back pain patients when compared to any control. The subgroups’ effects are less conclusive and no clear direction of the sustainability effect at short versus mid versus long-term, of the type of the comparator, or of the dose of the training is given. Low quality studies overestimated the effect of motor control exercises.

Background and Objectives: We systematically reviewed and delineated the existing evidence on sustainability effects of motor control exercises on pain intensity and disability in chronic low back pain patients when compared with an inactive or passive control group or with other exercises. Secondary aims were to reveal whether moderating factors like the time after training cessation, the study quality, and the training characteristics affect the potential sustainability effects. Methods: Relevant scientific databases (Medline, Web of Knowledge, Cochrane) were screened. Eligibility criteria for selecting studies: All RCTs und CTs on chronic (≥ 12/13 weeks) nonspecific low back pain, written in English or German and adopting a longitudinal core-specific/stabilizing sensorimotor control exercise intervention with at least one pain intensity and disability outcome assessment at follow-up (sustainability).
Results and Conclusions: From the 3,415 studies that were initially retrieved, 10 (2 CTs & 8 RCTs) on N=1081 patients were included in the review and analyses. Low to moderate quality evidence shows a sustainable positive effect of motor control exercise on pain (SMD=-.46, Z=2.9, p<.001) and disability (SMD=-.44, Z=2.5, p<.001) in low back pain patients when compared to any control. The subgroups' effects are less conclusive and no clear direction of the sustainability effect at short versus mid versus long-term, of the type of the comparator, or of the dose of the training is given. Low quality studies overestimated the effect of motor control exercises. This statement is required for submission and will appear in the published article if the submission is accepted. Please make sure it is accurate.

Unfunded studies
Enter: The author(s) received no specific funding for this work.  in particular proprioceptive, input, central nervous system integration and optimal motor control to 52 assure functional dynamic joint stability during perturbative situations, are key components of all the 53 training forms described above [10]. Studies using these appropriate muscle recruitment patterns and 54 timing key components as the adequate motor answer on perturbations of a (stable) system as train-55 ings principles may thus be pooled in analyses on motor control stabilisation exercises. As different 56 definitions and/or definitions with overlaps to non-dynamic motor control situations are often sum-57 marized under the term motor control (where, classically, pre-education on deep trunk muscles acti-58 vation and/or the control of deep muscles activation during exercising is done), the pooled effects of 59 (not only but also) long-term effects may have been over-or underestimated. The inclusion and exclusion criteria were defined with respect to PICO (population, intervention, con-83 trol/comparator, outcome. The criteria for both the participants and studies are displayed in Table 1. (stabili* OR sensorimotor OR "motor control" OR neuromuscular OR perturbation) AND (exercise OR 89 training OR therapy OR intervention OR treatment) AND ("low back pain" OR lumbalgia OR "lower 90 back pain" OR dorsalgia OR backache OR lumbago OR LBP OR "back pain"). 91 An initial exploratory electronic database search was conducted by two independent reviewers (JM 92 and DN) to define the final search terms. Both reviewers independently conducted the main research 93 afterwards. The herewith identified studies were screened for eligibility using 1) titles and 2) ab-94 stracts. The remaining full texts were assessed to ascertain whether they are fulfilling the inclusion 95 and not fulfilling the exclusion criteria. Consensus was used to address any disparities; a third re-96 viewer (N.N.) was asked, if necessary, to address any disparities. After study retrieval, additional studies were identified by manually searching through the reference list (cross-referencing) of the 98 selected articles. 99 Data extraction 100 The included studies were screened for common effect estimators (for pain intensity and disability). 101 Standard mean differences between intervention and comparator effect sizes were calculated based 102 on mean and standard deviation values for the respective scale. Data for the sustainability effects in 103 the short term (≥ 4 weeks ≤ 3 months), medium term (> 3 and ≤ 12months) and long term (> 12 104 months) after training cessation were collected. All data of interest (descriptive, PICO, interventional 105 details, study quality and risk of bias) were retrieved from the individual study data. For that pur-106 pose, a data extraction form, designed for this review, was used. One researcher recorded all the 107 pertinent data from the included articles and the other author independently reviewed the extracted 108 data for its relevance, accuracy and comprehensiveness. Consensus was used to address any dispari-109 ties; a third reviewer (N.N.) was asked, if necessary, to address any disparities. Authors of studies in-110 cluded in this review who have not reported sufficient details in the published manuscript were per-111 sonally addressed per e-mail for the provision of further data. Effect estimators (pain intensity and 112 disability) were primarily calculated using the visual analogue scale (VAS) or the numeric rating scale 113 (NRS) or sum score inherent of the scale/assessment tool (0-10 or 0-24 or 0-100), as the calculation 114 of the standard mean differences is scale-independent. For such data, only the direction (lower val-115 ues mean less pain, less disability) was normalized. For scale-dependent calculations (inverse 116 weighting), z-transformed (0-10) variables were used. Missing standard deviations for the differences 117 were imputed according to the procedure described in Follmann et al. [13]. 118 Study quality assessment 119 The methodological quality of all controlled trials included was assessed using the PEDro scale (11 120 criteria). The PEDro scale is a valid and reliable tool to assess the methodological quality of controlled 121 studies [14]. Each criterion was rated as 1 (definitely yes) or 0 (unclear or no); potential disagree-122 ments were discussed between the two authors and then resolved. 123 Risk of Bias within studies/outcomes 124 The two review authors (JM and DN) independently rated the risk of bias of the included studies, us-125 ing the Cochrane Collaboration's tool [15]. Following the Cochrane recommendations, bias was rated 126 outcome specific and not study specific (Cochrane Handbook Version 5.1.0, Chapter 8.7). The out-127 comes were graded for risk of bias in each of the following domains: sequence generation, allocation 128 concealment, blinding (participants, personnel, and outcome assessment), incomplete outcome data, 129 selective outcome reporting, and other sources of bias. Each item was rated as "high risk", "low risk", 130 or "unclear risk" of bias. Again, any disagreements were discussed between the raters. If a decision 131 could not be reached after discussion, a third reviewer (N.N.) was included to resolve any conflicts. If Cochrane Collaboration, 2014) was used for data analyses of the main effects. Standardised means 136 differences and sample sizes were used for data pooling. A random-effects meta-analysis model for 137 continuous outcomes was chosen. For variance description, 95 % confidence intervals were calcu-138 lated; data were displayed using Forrest-plots. To test for overall effects, Z-statistics at a 5 % alpha-139 error-probability level were calculated for: 1. Overall (main) effects and 2. Quantitative subgroup 140 analyses. For the overall effect calculation, each intervention group effects was calculated in contrast 141 to the comparator/control group. In studies with more than two MCE arms, more than one effect es-142 timator contributes to the main calculation. If more than one sustainability timepoint was assessed, 143 the mid-term sustainability effect was selected for the main analysis. For the quantitative subgroup 144 calculations, analyses were performed separately for 2a. sensitivity of time (short-term, mid-term, 145 and long-term sustainability), and 2b. sensitivity of comparator (inactive or passive vs. motor control stabilisation exercises (MCE) and other exercises vs. MCE). For variance description of the subgroup 147 analyses, 90 % confidence intervals were calculated; data were displayed using Forrest-plots. To test 148 for overall effects, Z-statistics at a 5 % alpha-error level were calculated. 149 Measures of treatment effects -assessment of heterogeneity  Study quality and risk of bias within studies (outcomes) 186 Both the study quality and risk of bias ratings are displayed in table 3. Overall study quality was 5/11 187 to 9/11 points, with a mean of 6.8. As the outcomes were assessed using self-reported questions 188 within the same questionnaires, the risk of bias was reported accumulated per study and not per out-189 come. Low quality evidence indicates that MCE has no larger short-term sustainability effect on pain inten-206 sity than a passive or inactive comparator. Low quality evidence indicates that MCE has a larger 207 short-term sustainability effect on disability than a passive or inactive comparator. 208 Low quality evidence indicates that MCE has no larger short-term sustainability effect on pain inten-209 sity and disability than other exercises. 210 Low quality evidence indicates that MCE has no larger mid-term sustainability effect on pain intensity 211 than a passive or inactive comparator. Moderate quality evidence indicates that MCE has no larger 212 mid-term sustainability effect on disability than a passive or inactive comparator. 213 Low to moderate quality evidence indicates that MCE has no larger mid-term sustainability effect on 214 pain intensity than other exercises. Low to moderate quality evidence indicates that MCE has no Moderate quality evidence indicates that MCE has no larger long-term sustainability effect on pain 217 intensity than a passive or inactive comparator. Moderate quality evidence indicates that MCE has no 218 larger long-term sustainability effect on disability than a passive or inactive comparator. 219 Low to moderate quality evidence indicates that MCE has a larger long-term sustainability effect on 220 pain intensity than other exercises. Low to moderate quality evidence indicates that MCE has no 221 larger long-term sustainability effect on disability than other exercises. 222 Individual studies: training characteristics 223 The results of the five meta-regressions as sensitivity analyses are highlighted in Table 5. The training  230 duration, frequency, total trainings dose and training-to-sustainability ratio showed no impact on the 231 effect size of the primary outcome pain. 232 The PEDro sum score was negatively associated with the effect size, a study with a score-decrease of 233 1 point shows an increase in the effect size of .24. Figure 9 illustrates this association. 234

Risk of bias across studies 235
The risk of bias across studies (publication bias) is, by means of a funnel plot, highlighted in Figure 10. Low to moderate quality evidence indicates that MCE has a larger overall sustainability effect on pain 242 intensity and disability reduction than a passive, inactive or other exercise comparator. 243 Subgroup sensitivity analyses revealed with low quality evidence that, in the short-term sustainabil-244 ity, MCE has no larger short-term effect on pain intensity than a passive or inactive comparator or 245 than other exercises. Low quality evidence indicates that MCE has a larger short-term sustainability 246 effect on disability, but not on pain intensity, than a passive or inactive comparator. In the mid-term 247 sustainability, low to moderate quality evidence indicates that MCE has no larger effect on pain in-248 tensity or disability than a passive or inactive comparator or than other exercises. Moderate quality 249 evidence further indicates that MCE has no larger long-term sustainability effect on disability than a 250 passive or inactive comparator but a larger long-term sustainability effect on pain intensity than 251 other exercises. Low to moderate quality evidence indicates that MCE has no larger long-term sus-252 tainability effect on disability than other exercises or passive or inactive treatments. 253 The subsequent meta-regression demonstrated that the training duration, frequency, total trainings 254 dose and training-to-sustainability ratio has no impact on the effect size of the primary outcome 255 pain. The PEDro sum score was negatively associated with the effect size and studies with lower qual-256 ity may overestimate the (sustainability) effects of MCE on pain intensity and disability reduction. Overall, MCE seems to be slightly more sustainable or at least equivalent to other exercises and 282 slightly more sustainable than passive or inactive treatments in terms of pain intensity and disability 283 reduction. Although, derived from the quality of evidence of the findings, no grade A recommenda-284 tion can be provided, but MCE seems to be both effective and safe in the treatment of low back pain.    Table 3: Study quality and risk of bias. PEDro-scale-items: 1) eligibility criteria were specified, 2) participants were randomly allocated to groups, 3) allocation was concealed, 4) the groups were 435 similar at baseline regarding the most important prognostic indicators, 5) there was blinding of all participants, 6) there was blinding of all therapists who administered the therapy, 7) there was 436 blinding of all assessors who measured at least one key outcome, 8) measures of at least one key outcome were obtained from more than 85% of the subjects initially allocated to groups, 9) all 437 subjects for whom outcome measures were available received the treatment or control condition as allocated or, where this was not the case, data for at least one key outcome was analysed by 438 "intention to treat", 10) the results of between-group statistical comparisons are reported for at least one key outcome, 11) the study provides both point measures and measures of variability for 439 at least one key outcome.

Critchley, 2007
Spinal Stabil N.A.: individual transversus abdominis and lumbar multifidus muscle training followed by group exercises that challenged spinal stability. Exercises were tailored to assessment findings and progressed within participants' ability to maintain a stable and minimally painful spine. The exercise program aimed to improve trunk muscle motor control Physio,